In particular, the present invention relates to a dispenser of the type comprising a containment body with substantially axial-symmetric geometry, internally hollow and able to be inserted in the neck of a bottle.
The containment body is provided in a first end with an orifice for the entry of the liquid product present in the bottle. Said orifice is opened or closed by a ball free to slide within the containment body, in particular within a dosing chamber included therein.
The dosing chamber is defined by the space present between a piston, guided by an internally hollow stem, able to slide within the containment body and the bottom portion (where the orifice is positioned) of the containment body.
Between piston and stem are present means for opening and closing the inner cavity of the stem in such a way as selectively to place in fluid communication the interior of the stem with the dosing chamber.
The stem is guided in its travel by a retaining ring, integral with the containment body, which also serves the abutment function for the travel of the piston.
In other words, the retaining ring defines the upper limit of the dosing chamber, preventing the piston from being able to exit from the dosing chamber itself.
When the piston creates an overpressure within the dosing chamber, the cavity of the stem is in fluid communication with the dosing chamber and the fluid present in the dosing chamber rises along the stem and is dispensed by a spout associated therewith.
In this configuration, the ball is lowered and occludes the aforementioned orifice because of the overpressure in the dosing chamber.
When the piston creates a vacuum within the dosing chamber the cavity of the stem is not in fluid communication with the dosing chamber and fluid is moved from the bottle into the dosing chamber.
In this configuration, the ball is raised and leaves open the aforementioned orifice because of the vacuum in the dosing chamber.
In this type of dispenser, the sliding of the piston within the containment body takes place contrasting the action of a spring whose function is to maintain the piston in raised position.
In particular, exercising a compression action on the stem, the piston slides within the dosing chamber, reducing its dimensions and hence creating an overpressure within it.
Ceasing the compression action on the stem, the aforementioned spring brings the piston back to the raised position, expanding the dimensions of the dosing chamber and hence creating a vacuum therein.
In these types of prior art dispensers, it is often preferred to prevent the spring from lying in the dosing chamber (thus acting between the stem or the piston and the bottom of the dosing chamber), in such a way as to prevent the spring from coming into contact with the fluid to be dispensed (which, as stated, moves from the bottle to the dosing chamber and thence to the dispensing spout through the cavity of the stem).
For this purpose, the spring is placed in so-called “external” position, in such a way that it acts between the stem and the retaining ring.
Therefore, the compression force exercised on the stem is unloaded on the retaining ring and thence it is transmitted to the containment body, and lastly to the bottle.
It should be noted that the retaining ring is made integral with the containment body thanks to the insertion of an annular edge of the ring within an undercut obtained in the containment body.
The retaining ring shall also assure a fluid tightness between its own outer wall and the wall of the containment body, to prevent the liquid contained in the bottle from escaping because of the overpressures that may be generated between the interior of the bottle and the environment in occasional situations (depressurized environment) or accidental situations (crushing of the bottle).
However, the prior art dispensers described above present some drawbacks.
During the operations for mounting the dispenser, in particular during the fitting of the dispensing spout, the compression forces necessary to insert the dispenser on the stem are contrasted by the retaining ring, i.e. they are unloaded on the containment body through the coupling between retaining ring and containment body itself.
In these conditions, to prevent an excessive pressure of the stem from thrusting the piston too deep into the dosing chamber, damaging it, the spring positioned between stem and retaining ring is arranged in such a way that the configuration of maximum compression of the spring coincides with the position of the maximum insertion of the piston in the dosing chamber (i.e. with the position of maximum lowering of the piston), with the disadvantage of an additional constraint in the selection of design parameters, e.g. diameter and number of coils, and the consequent use of oversized or excessively rigid springs, with respect to the simple function of exercising a returning action on the piston.
With solutions of this kind, if an excessive assembly force is exercised, the retaining ring could be damaged and not assure its functionalities (especially the fluid tightness with the inner wall of the containment body) for which it was designed.